JPS5916770A - Thermal recorder - Google Patents

Abstract

PURPOSE:To enable to record in a constant density even when a power source voltage fluctuates, by providing a counting part for controlling the recording time by which a recording signal determining the total quantity of energy supplied to a thermal head is changed in accordance with a set point. CONSTITUTION:An astable power source voltage is impressed on a multiplier 13, and when an output voltage of the multiplier 13 is raised, an output from a monostable multivibrator (MM) 16 is made to be high by an output signal from a voltage comparator 14. When a flip-floP circuit (FF) 11 is reset through an AND circuit 18 and an OR circuit 10 to open a switch SW1, the voltage on a line l1 is gradually lowered. When the voltage is lowered to a predetermined value, the switch SW1 is again closed by an output form a voltage comparator 15, and an impressed pulse voltage is supplied to the thermal head through a terminal T2. During this operation, the output voltage is supplied also to a voltage control oscillator (VCO) 16, the output frequencely thereof is shifted to the higher or lower side according as the voltage is raised or lowered, resulting in that a carrier signal from the counting part is accelerated or decelerated, and the energy-impressing time is controlled by the frequency dividing ratio. Accordingly, it is possible to record in an arbitrarily selected constant density even when the power source voltage fluctuates.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a thermal head is brought into contact with a recording medium directly or via an ink sheet, and the thermal head is heated based on an electric signal, whereby an image or the like is formed on the recording medium. The present invention relates to a thermal recording device.

A thermal recording device is composed of a thermal recording section and a paper feeding section, and the present invention particularly relates to the thermal recording section.

The thermal recording method is a method in which a heating element (thermal head) is brought into contact with the recording material directly or through an ink sheet, and the thermal head is heated, thereby applying heat to the ink sheet or thermal paper. This is a method in which only a portion of the image is recorded on the recording medium.

The external appearance of the thermal head 1 includes a printed circuit board 2.3 as shown in FIG. 1, and its main parts are as shown in FIG.
It has a thermal insulating layer 5 on a ceramic substrate, a heating element layer 6 provided thereon, a large number of counter electrodes 7, 8 laminated, and covered with a surface protection layer.

By applying a predetermined pulse pressure (applying force) between the opposing electrodes 7 and 8, the heating element layer 6 selectively generates heat. At this time, if the size of the recording paper is B4 size and the thermal head is ado4m, 2[)4
A counter electrode of 8 dat is required.

For the above-mentioned heat generation, approximately 0.6 to 1 per dot is required.
A power of about W is required, and even if recording is to be performed twice, a large source capacity of 600.times.-7 KW is required.

Here, to describe the relationship between the temperature of the thermal head and the density of an image recorded on a recording medium (particularly color-forming thermal paper), the higher the temperature of the thermal head, the more the image appears.
The lower the temperature, the more visible it becomes. Therefore, in order to maintain a constant density of an image recorded on a recording medium, it is necessary to maintain the thermal head at a predetermined temperature.

However, when the power supply voltage fluctuates, the jJo pulse voltage changes accordingly, and the power supplied to the thermal head fluctuates, making it impossible to maintain the thermal head at a predetermined temperature and causing the image appearing on the recording medium to deteriorate. There may be unevenness.

Fluctuations in the power supply voltage appear as they are in the shading of the image. Therefore, in order to record uniform images, etc., a stable power source is required. However, the situation is correct 6
A stable power supply of 00 W to IKW is extremely sophisticated.

Conventionally, in order to perform thermal recording, a voltage of +17 width is applied to the thermal head facing the thermal head, and a certain peak temperature I is applied.
t(θp)−2 years, by which recording was performed (
′! (See Figure 3). This curve of temperature change over time can be expressed mathematically as follows.

Temperature is o ('c), heat leakage f'1 - resistance is R (0C
/W), heat capacity is C (JloC), applied force is q
(W), and let Q(J) be the heat cycle, when the temperature decreases, even if it is 0° (0C) when t=0, θ-
θ. It is represented by CR.

It has been found that a curve similar to this curve of temperature change over time can be obtained with an electric circuit. In other words, at least the heat capacity and thermal resistance of the thermal head and the recording medium (including the heat-melting ink film of the thermal transfer type) are measured in advance, and the combined heat capacity i Cs
and the composite thermal resistance dynamic, with a capacitor (μJ
10C is ttli', ') and resistance (0C/W is Ω)
This constitutes an electric circuit (simulation circuit), and the above curve can be obtained electrically by this circuit. This electric circuit is used as a simulation circuit, and the voltage obtained by this circuit is used to control the time of the applied pulse voltage applied to the thermal head, and when a predetermined power or applied energy amount is reached, this is calculated and the applied pulse is applied. The first is to stop the voltage supply.

Therefore, this simulation circuit is a very effective means for obtaining a record of a predetermined number of degrees with respect to fluctuations in the source pressure. However, when recording an image or the like obtained by this simulation circuit, only a certain limited density can be obtained, and the density cannot be freely selected.

Depending on the purpose of the recording medium, it may not be possible to meet the request for recording an image or the like to be darker or lighter overall.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal recording device that can freely select the density of images, prints, etc. recorded on a recording medium even if there are fluctuations in power supply voltage.

That is, in the thermal recording device according to the present invention, a thermal head is brought into contact with a recording medium directly or via an ink sheet, and the thermal head is heated based on a recording signal to record information on the recording medium. At this time, it is obtained from at least the heat capacity and thermal resistance of at least one of the thermal head, the recording medium, and the ink sheet. A simulation circuit is provided to control the temperature of the thermal head based on a curve corresponding to a temperature rise of the thermal head, and after the thermal head reaches a predetermined temperature, a recording signal for heating the thermal head is intermittent. , the total energy applied to the thermal head 1 is a predetermined heat l.
In a thermal recording device that calculates that heating of the thermal head has been reached and stops heating the thermal head, a recording signal for controlling the recording time to change the recording signal that determines the total energy applied to the thermal head according to a set value. The device is characterized in that it is provided with a counting section.

Therefore, according to the present invention, regardless of fluctuations in the power supply voltage,
It is possible to obtain recordings of uniform, constant, and free density.

Next, embodiments of the present invention will be described in detail.

Clarify the relationship between color density of thermal paper and applied energy. In other words, it is necessary to clarify how much applied energy is required to obtain a record of an image or the like with a density of (See Figure 4). That is, the stage from which the density of recording an image or the like changes from white to black is divided into a certain width, and the required applied energy value is determined for each of the divided densities. To explain with reference to FIG. 4, for example, to record an image with a color density of 0.5, approximately 0.49 mJ of energy is required;
．． To record an image of 0, etc.

Q: It turns out that 64 mJ of energy is required. After determining the energy values required for each of the divided concentrations, these energy values are stored in advance in a ROM (read only memory). This ROM is connected to a preset counter, and when a command is given for the desired concentration, the preset counter reads the required energy value from the ROM, and when the energy supplied to the thermal head reaches that value, the applied energy is applied. Stop the pulse voltage. This makes it possible to record an image or the like with a uniform, constant, and desired density (halftone at \j).

In this embodiment, the counting section is composed of a ROM and a preset counter, but it can also be composed of another timer.

Next, a circuit diagram of a thermal recording apparatus including the above-mentioned simulation circuit of the present invention and a counting section for printing time control will be explained with reference to FIG.

In FIG. 5, an unstable power supply voltage V in is supplied to the input terminal TIvC. A pulsed start signal V1 is supplied to the terminal T3. The start signal v1 is supplied to the set terminal of the flip-flop circuit (hereinafter referred to as FF) 11 via the OR circuit 9 in FIG. And T3 is also connected to the preset counter f'L, v
The signal i becomes a command to start counting. FF11. FF
By inputting Vl to the set terminal of FF1
1. The voltage level of the output Q of the FF12 is HT (level HT).Then, the output of the FF11 causes the analog switch 8 to
device is switched on. In addition, analog switch 8
The structure is shown as a mechanical structure for convenience of explanation. The applied voltage vin is obtained from the multiplier 1r5 fL, and this voltage V
is supplied to line 11 via switch SW1. The capacitor O and the resistor constitute the above-mentioned simulation circuit. The voltage V on line ll is determined by voltage comparator 141
b is supplied to each non-inverting input terminal. Note that the voltage V obtained from the multiplier 13 is also supplied to a voltage control oscillator (hereinafter referred to as VCO) 16.

- 10,000, the reference voltage VQ is supplied to the terminal T4, and the voltage Vθ2, which is slightly lower than the reference voltage, is supplied to the terminal 1.
It's true.

The voltage level on line ll gradually increases until voltage VO1
When this reaches, an output signal is obtained from the pressure comparator 14, and in synchronization with this, the output signal of the monostable multivibrator (hereinafter referred to as MM) 16 becomes H level. Then, each input terminal asb*c of the AND circuit 1 becomes H level, and the output signal also becomes H level. AND circuit 1
The day output signal is connected to the reset terminal of the FF 11 via the OR circuit 10, and the Q output of the FF 11 becomes L level. Then, the analog switch Sw1 is turned off, and the voltage V on the line ll gradually decreases. When the '1 voltage V decreases to the voltage Ve2ii, an output signal is obtained from the voltage comparator 15, and the output of the MM17 becomes H level.

Each input terminal abIc of the AND circuit 19 is at H level, and the output signal is also at - level. The output signal of the AND circuit 19 is supplied to the set terminal of the FF 11 via the OR circuit 9.

When FFMl is switched back to the set state, the analog switch SWl is turned on again. At this time, the voltage V on line 11 has a waveform as shown in Fig. 6 (1).

An applied pulse voltage is supplied to the thermal head 1 from this bundling and output terminal T2.

Incidentally, lIj]b v c O where the above operation is performed
Voltage V is supplied to 16, and when ■ rises, VC
The output frequency of O16 gradually shifts to a higher frequency, and when ■ is low, shifts to a lower frequency.

Since the output signal of the VCO 16 shifts to a high frequency signal in proportion to the input terminal, the higher ■ is, the more the counter 20
If the output time of the carry signal outputted from n is earlier, the output time will be delayed if n is low. Counting part 2
The time of applied energy is controlled by the frequency division ratio N of 0 and the frequency of the output signal of the vCO 16, and when a predetermined energy is reached, a carry signal is output from the counting section 20. The carry signal causes FFI 1. The FF12 is switched to the reset state, and the analog switch 5w14 is switched to the off state. This completes heating and returns to the initial state.
)do.

Here, in order to obtain a record of the desired degree of image, etc., before pressing the switch that generates the start signal η, press the finger 11 on the preset counter that constitutes the counting section.
to play. The energy value required to record an image with the desired density and the energy V supplied to the thermal head.
Ghee (when direct and direct become equal)

Preset counter 22 to issue a carry signal.
Therefore, it is set to . The grisset counter 22 is
The energy value required for that concentration is read from the ROM 21 connected to the preset counter 22. R
A desired gradation signal T6 is given to OMQl at the timing of T3. When the energy value supplied to the thermal head becomes equal to the energy value read from the ROM 21, a carry signal rL is output from the preset counter 22, and this signal causes the FF 11. FF
12 is switched to the reset state and the analog switch S
Wl is also switched to the off state. Heating ends here,
A record of an image or the like having a specified density is obtained based on changes in the applied pulse width. 3. In the ROM 21, for example, 20.21.22. A 4-bit gradation signal 1t for 14 in 23 is added, and a corresponding binary 1 blue signal is stored in memory.

Note that the inverting input terminal V of the voltage comparator 14 in Fig. 85 is
FIG. 6FA) A voltage corresponding to the voltage Vθl indicated by IfC is supplied. Moreover, the inverting input terminal of the voltage comparator 15 has
A voltage corresponding to voltage vo2 not shown in FIG. 6(A) is supplied. FIG. 6(A) shows the thermal response characteristics when the applied voltage Vin is high, and the timing controller (not shown)
From this, an applied pulse Vout as shown in FIG. 6(B) is obtained. Note that the temperature 01 is, for example, about 3000C, and the temperature θ2 is, for example, about 28D'C.

Then, an applied pulse Vout as shown in FIG. 6(B) is obtained from the output terminal T2 and supplied to the thermal head. By the way, if the total amount of energy applied by the applied pulse Vout is E, this is determined by the product of the applied power W and the application time S.

I mean.

E=W-8(J) The resistance value of the heating element is rt H, applied i Ek-V in
Assuming that V is the above equation, E=V2/RH, 5(J) From this equation, it can be understood that in order to obtain a constant printing quality, it is sufficient to keep E constant.

In this equation, since s 1 /RH is a constant, E can be made constant by changing S in response to fluctuations in V. In other words, even if the applied voltage Vln is simply full-wave rectified and then incompletely smoothed and includes ripple voltage, E can be kept constant by changing S in response to voltage level fluctuations. . As a result, even if there are fluctuations in the applied voltage, that is, even if an unregulated power supply is used, stable thermal recording can be performed by following this change, and there is no possibility of distortion or cracks occurring in the thermal head or burnout of the heating element. It is possible to prevent unexpected situations from occurring.

Therefore, it is possible to prevent changes in the heating resistance value due to changes in the applied voltage and to shorten the life of the thermal head.

Note that the invention can be applied not only to recording on the above-mentioned thermal paper but also to transfer type thermal recording using an ink sheet as described above.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the shape of the thermal head. Figure 2 is a sectional view of the main parts showing the structure of the thermal head. Figure 3 is a characteristic diagram showing the relationship between the 4 pressures applied to the thermal head and temperature. Figure 4 shows the density characteristics of thermal paper. Figure 5 shows the entire thermal recording device equipped with a simulation circuit and a counting section for controlling printing time. Figure 6 shows the circuit diagram above. FIG. 3 is a diagram showing changes in voltage. Note that the code used in one drawing is 9, R11Ic.
,...Capacitor and resistor (I5) constituting the simulation circuit 1...-Thermal head 2, 3 @111111 Printed circuit board 4110/Ceramic board 5/Oe disconnected wire-6...-Heating element layer 7+B ...Counter electrode 9+'100...OR circuit 11112"...Flip-flop circuit 13...Fist multiplier 14115...Voltage comparator 16117...Monostable multi-node ibrator 18.
196...AND circuit 200...Reduction part 21...ROM (read only memory)
220: Preset counter. Agent Patent Attorney Hiroshi Aisaka 1G Figure 3 Figure 1 to Figure 6■...Pa. I died,

Claims (1)

[Claims] t When recording information on the recording material by bringing the thermal head into contact with the recording material directly or via an ink sheet and heating the thermal head based on a recording signal, the thermal head and the recording material and a simulation circuit that controls the temperature of the thermal head based on a curve corresponding to a temperature rise of the thermal head obtained from at least one of the heat capacity and thermal resistance of at least one of the ink sheets, After the predetermined temperature is reached, the recording signal for heating the thermal head is intermittent, and when it is calculated that the total amount of energy applied to the thermal head has reached a predetermined value, the heating of the thermal head is started. What is claimed is: 1. A thermal recording device that stops, further comprising a recording time control counting unit for changing a recording signal that determines the total amount of energy applied to the thermal head in accordance with a set value.